Wave guide coupler



July 25, 1950 E. M. PURCELL 2,516,528

WAVE GUIDE COUPLER Filed March 2l, 1944 CRYSTAL DETECTOR INVENTOR. EDM/4R0 M PUR CEL L Patented July 25,Y 1950 by mesne assignments, to.- tlreUnited States off America. as representeds` by thef- Secretary of- War Application March=21, 1944, Serial No. 527,426

3 Claims'. (Cl. 17-8-44) This inventionl relates to a detector adapted to determine standing high frequency wave ratios in hollow wave guides.

In a test device of this character, a. detector probe is movably disposed` within a wave carrying guide, and electric intensity values are:` determined at various points along the guide; The principal object of the invention, therefore, is to provide means for moving a test probe in the guide through small butv measurable distancesA in such a manner as to avoid error causing backlash `and undesired relative motion of the detector parts with respect to. the guide.

To accomplish this object, a test' probe is rigidly carried by an associated pickup wave: guide which is pivotally mounted with respect to the wave carrying guide. A circular curveis provided in the latter guide, and the probe. carrying pickup guide is pivoted at the center of curvature, so that the probe may be moved axially: within the arcuate guide, the pivoted structure thus being maintained in unvaryin'g radiali' relation with the guide. The probe, which extends into the arcuate guide through a slot therein, is carried by the shorter of two arms' comprising the pickup guide, the other and l'onger arm being arranged to move over a calibrated! scale. Thus the longer arm may be moved a suitable distance measured on the scale, and the probe K will be moved along the guideinterior a smallerS tional dimensions as guide IIL, is: pivotally mounted for angular rotation. atl the center of curvature I6 of arcuate structure II-. Guide I5 is divided by the pivot point intoT twoarms of unequal length. The shorter arm |51t extends into operable relationship with curved structure II and terminates justshort of the wave guide'. A metallictest. probe IL8 extends from-1 the free end of'arm IIv into the curved section of wave guide IIl' (best shown in Fig; 3)'. The otheriand'longer armofpickup' guide I5 terminatessin anadjusting pointer 2'0 varranged to move-over a calibrated scale 2I. Thus pointer 2llfmay be moved a'. predetermined distance, measured'fonf scale 2|, and test probe I8, carried by the opposite'end of guide I5, will be moved av proportionate distance-along guide I0. Ir" desired, scale ZI may be-calibrated to read" directly the distance moved by they probe.

A section of rectangular waveguide 25 extends at rightangles from thelonger arm to a detector 2li, whichl may be the usual crystal type detector. Leads 2l connect to a suitableA meter (not shown) for indicating the intensity of detected energy. Inorder to properly match the impedance` of detector 26, a shorting plunger 3i) is disposed within the longer arm of guide I5. Plungier 3B movable along the guide interior to vary: guide length, is xed in proper positionVr by4` an associated thumb screw 3 I. Y

Figs. 2' and 2A illustrate a suggested method for constructing the circular bend I I for use with the invention. A metal disc 35 is turnedztoprovide annular flanges 36' and 3l (best shown in for constructing the above-mentioned circular FigJl is a sectional View on the liney 4'41 015140.

Fig. 3; Fig. 5 is a sectional View on the-line: 5--5 of Fig. 3; and Figs. 6, 7, and' Bare sectionalviews on the lines 5 6, 'II-'l' and 3"-8, respectively; of

Fig. 3, showing the electric vectors atY various l points in the pickup wave guide. it

Fig. 2). Prepared disc 35 is then cut in accordance with the dotted lines" (Fig. 2A) so as to provide segments 38 and 39. Segment 39' is inverted upon segment 35, as shown, and the two parts are fixed together. Thus, perf-ect symmetryy is maintained for all parts about the center of curvature I6. It will be noted' that ila-nge 3l' is slightly shorter than flange 35 so that a narrow space exists between opposing flanges 31 when the two segments areV xed together. Test probe I 8" extends into the wave guide i through this narrow space thus providedv in a longer guide side.

Referring now' to Fig. 3, pickup Wave guide I5 is pivotally mounted at'y the center ofi curvature i6 of disc segment 38. A rectangular collar 40 slidably receives guide I5 and supports said guide at the pivot point. A bearing plate 4| is fixed to the top of collar 40 by screws 42. The degree of coupling between pickup guide I5 and guide I0 is determined by the distance that probe I8 is inserted into guide I0. The coupling may I desired TEoi.

be varied by sliding guide i in collar 40. After guide I5 is adjustably positioned in collar 40 for proper coupling, screws 42 lock it in place. Thus, guide I5 is longitudinally slidable with respect to the pivot point so that test probe I8 mounted at the guide end may be pre-set at different radial positions within test guide I0. A fixed supporting member 43 (Fig. 5) is rigidly associated with plate 38 at a point away from the center of curvature, a portion l44 thereof eX- tending above the plate and over the vcenter of curvature. Member 43 is secured to the plate by ange 45 and screws 46. Plate 38, `collar 40, bearing plate 4l and iixed portion 44 have appropriate collinear recesses to receive and retain ball bearings 41 and 48, which pivotally support Wave guide i5 at thecenter of curvature I6 of the arcuate guide.

In order to provide electromagnetic coupling between pickup guide I5 and guide Hl, insulation 50`is disposed-inthe end of guide l5 adjacent curved'structure Hu Insulation 50, which may be polystyrene, is rectangular in cross section,the long'dirnension'thereoi being equal to the long sectional dimension of lthe wave guide, and" its shorter dimension being one-half the short dimension of the guide.

Probe I8 is embedded in a `reduced section 5i of the insulation which extends through the space provided in the arcuate guide side. The length of block 50 is such that a 180 phase difference 'must be produced at the end. *While this particular method of coupling is -will be as shown in Fig. 6.' Upon reaching the end ci the insulation, the difference in phase *velocities 'between air and the insulation will have caused a 180 difference in relative phase position ofthe traveling potentials which-resultsI in the distribution of Fig. 7. This distribution at the end causes proper excitation of guide I5 as shown in Fig. 8 wherein the wave mode is the Having thus described the invention, what I claim as new and desire to secure by Letters Pat- 4ent is:

l.-A' rneans for coupling rectangular wave guides together for transfer of wave energy, one

of saidguides having an opening in` one of itsy equal to 'half-the narrow side of the guide, the

length of said block being such as to produce a phase shift in block conducted waves as.

compared to waves traveling in the guide portion adjacent said block, and a probe carried centrally L of said last guide by said block, said probe extending through said opening into said iirst guide k4 1 and being disposed therein in the direction of the electric eld.

2. A means for coupling rectangular wave guides, one of said guides having an arcuate portion, said portion havingl a longitudinal slot in one of the wider sides thereof, the other guide having an end disposed'adjacent said slot, a rectangular block lof insulation material within the end of said last-named guide, said block having in cross-section a wide sectional dimension corresponding to the wide side of the guide and a narrow dimension equal to half the narrow side of the guide, the length of said block being such as to produce a 180 phase shift in waves traveling through said block relative to waves traveling in the guide portion adjacent said block, a probe carried centrally of said last guide by said block, said probe extending through said slot to said rst guide and being disposed therein in the direction of the electric "eld, said last guide being pivotly mounted at the center'of curvature of said arcuate portion whereby said probe may be positioned at different radialpoints in said arcuate portion.

- 3.v In a standing wave detector wherein energy is coupled from a rst rectangular guide, having an arcuate portion and a longitudinal slot'in one oi the wide sides of said portion, to a second rectangular guide having an end disposed adjacent said slot, said second guide being pivotly mounted at the center of curvature of said arcuate portion, a probe extending through said slot to said first guide for coupling said guides at different radial points in said arcuate portion, saidv probe being disposed therein in the direction of the electric eld, the combination with said second guide of a rectangular block of insulation material posi- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,426,207 McDufE Aug. 15, 1922 1,979,912 Stirling Nov. 6, 1934 2,088,106 Frank July 27, 193'? 2,106,713 Bowen Feb. 1, 1938 2,113,675 Brown Apr. 12, 1938 2,129,669 Bowen Sept. 13, 1933 2,191,271 Carter Feb. 20, 1940 2,203,984 Deters June 11, 1940 2,359,869 Moore Oct. 10, 1944 2,403,289 Korman July 2, 1946 2,404,797 I-lansen July 30, 1946 2,407,267 Ginzton Sept. 10, 1946 2,433,011 Zaleski Dec. 23, 1947 

